Cameron Douglas with his actor father Michael Douglas in 2009. Photo: AFP/Getty Images

Greed may be good, but seeing your son in the slammer — not so much.

Famed “Wall Street” actor Michael Douglas sat through 40 minutes of appeals court arguments this morning in hopes that his drug-addicted eldest son, Cameron, will win a break on his 4-1/2 year sentence for possessing drugs in jail.

“There’s not much to say — it’s on appeal,” Douglas said before hopping into a black Jaguar sedan outside the Manhattan federal courthouse.

During the court session, Douglas sat near the back of the courtroom, next to Cameron’s criminal-defense lawyer and down the row from ex-wife Diandra, who is Cameron’s mom.

The long-divorced couple recently feuded over Diandra’s failed claim to a share of Michael’s millions from “Wall Street 2: Money Never Sleeps,” in which he reprised his Oscar-winning role as corporate raider Gordon Gekko.

But they huddled together in the hallway for nearly an hour after listening to this morning’s legal arguments, which ran twice as long as scheduled.

Three judges with the US Second Circuit Court of Appeals peppered lawyers on both sides with questions about the unusually harsh 4 1/2-year punishment Cameron got after he was caught with small amounts of heroin and Suboxone, a prescription drug used to treat opiate addiction behind bars.

Presiding Judge Gerard Lynch noted that Cameron earlier got a sweetheart, five-year plea deal for selling out his suppliers after he was caught dealing meth, and that even with the extra 4 1/2 years, he was still serving less time than the mandatory, 10-year minimum he would have faced without cooperating.

The panel reserved decision afterward.

There was no mention of the broken leg and finger that Cameron recently suffered behind bars, which The Post reported came after a crime-family captain bounty put a $100 bounty on him for turning rat.